Linear block copolymers of polystyrene and polydimethylsiloxane have been synthesized, both by graft and block copolymerization. In block copolymerization of such linear polymers, polystyrene (PS) is produced by anionic polymerization with an organo lithium initiator and the living polymer (PS-Li+) created thereby is reacted with hexamethylcyclotrisiloxane, (Me.sub.2 SiO).sub.3, in the presence of a polar promoter wherein a block of polydimethylsiloxane (PDMS) grows on the end of the living vinyl aromatic hydrocarbon polymer block.
Typically, saturated versions of unsaturated polymers are obtained by hydrogenation of the product polymer. This often leads to slow kinetics, high viscosities, polymer degradation, etc. It would be highly advantageous to have a method for producing saturated versions of unsaturated polymers which do not require the hydrogenation of the product polymer itself. In one embodiment of the present invention, such a method is provided.
Hydrogenation of aromatic components of polymers is known to be difficult. In fact, in the case of block copolymers of polystyrenes and polydienes, it is well known that the polydienes can be almost completely hydrogenated without affecting the polystyrene significantly. Polystyrene/polysiloxane block copolymers are known, including polysiloxane blocks which contain aromatic functionality. Saturated versions of such polymers cannot be made by conventional polymerization techniques. The present invention provides a method for producing saturated polymers from these polysiloxane copolymers.